One type of carrier often used to package twelve or twenty-four beverage cans is the sleeve-type carrier. Such a carrier is enclosed on all sides and is typically formed from a generally rectangular paperboard production blank which has been folded and glued by the blank manufacturer to form an interim sleeve-like product consisting of connected top, bottom and side panels. This interim product is shipped in flat collapsed form to a bottling plant where, through use of an automatic packaging machine, the collapsed sleeve is opened into its full sleeve shape, cans are inserted into the sleeve, and the end panels of the carrier are formed by gluing together flaps which are foldably connected to the blank.
More specifically, after the beverage cans have been inserted through the open ends of the sleeve the first step in forming the end panels of the package is to first fold the dust flaps toward each other. Prior to the folding operation the dust flaps extend outwardly from the vertically aligned leading and trailing panels as the sleeve moves along its path of travel through the packaging machine. Subsequently the end flaps extending outwardly from the upper and lower panels of the sleeve are folded toward each other and glued to the dust flaps to complete the formation of the end panels.
The leading dust flaps conventionally are folded back by stationary rails or rods which contact the flaps and force them back and inwardly as the carrier sleeve moves past the rails. This has been found to be an efficient, practical way to carry out this operation and is not in need of change. By the same token, the downward and upward folding of the end flaps can be efficiently carried out by stationary rails or other simple folding apparatus.
The method of folding the trailing dust flaps forward, however, is a different matter. Because the flaps have to be folded in the same direction as the movement of the carrier sleeve, static rails cannot be used. Over the years a number of different types of flap closing methods have been employed, but in general they have suffered from the problem of being too complicated. When mechanisms designed to operate at the extremely high speeds of a modern packaging machine are too complicated, depending on a number of moving parts required to have precisely timed operations in order to mesh with other operations of the machine, the possibility of a breakdown is increased. For example, the use of a tucker wheel mounted to rotate about a vertical axis, which folds in the trailing flap as the carrier sleeve moves by, requires a drive mechanism, a clutch, a tuning sprocket to enable adjustments to be made, a gear box and the tucker assembly itself. Obviously, the cost of such apparatus or of other still more complicated folding equipment is high and maintenance of the equipment is demanding.
It would therefore be desirable to have a more simple, yet highly efficient method of folding the trailing dust flaps of a sleeve-type carrier during the packaging operation.